Staff at Jobcentres have an "alarming" lack of confidence dealing with disabled people just weeks ahead of new welfare reforms coming into force, campaigners have warned.
Phil Reynolds, co-chairman of the Disability Benefits Consortium, said it was important disabled people were not "shoehorned" back into work as a result of the Government's new claimant commitment.
It will be introduced for employment and support allowance (ESA) claimants in September, setting out activities they must do to get their benefits.
Research by the Department for Work and Pensions (DWP) found some Jobcentre work coaches found it "daunting" and "uncomfortable" working with ESA claimants, and felt they needed extra training on things like mental health.
Claimant commitments are already used for those claiming jobseeker's allowance and universal credit, but will be rolled out next month for ESA claimants, who are unable to work due to illness or disability.
DWP said claimants and work coaches had responded positively during the trial and that "thorough training" was given on how to support people with disabilities and long term health conditions.
Mr Reynolds, who is also senior policy and campaigns adviser at Parkinson's UK, called for an urgent review of the policy before it is introduced.
"These findings show an alarming lack of confidence from work coaches when dealing with the complex needs of disabled people," he told the Press Association.
"A good understanding of degenerative conditions like Parkinson's is vital to ensure the process is fit for purpose, that disabled people receive the support they desperately need and aren't shoehorned into harmful back-to-work activity if that isn't right for them.
"It's imperative that the DWP learns lessons from this research, to ensure that these interventions are in the best interests of disabled people and do not create unnecessary, additional barriers that result in little or no impact on a person's ability to get back into work."
The research by DWP was commissioned on the back of trials of the new programme in 2016.
Published this week, it found some less experienced work coaches had expressed "a lack of confidence, a need for training, and an apprehension towards working with ESA claimants".
There was concern about the "strong work focus" of the claimant commitment, and a need to consider "a bigger picture" where claimants may benefit from smaller measures not related to work.
The report found the claimant commitment was sometimes viewed to be "pushing work when the claimant was not ready for work at that time".
There was some positive feedback, with work coaches saying it helped them maintain contact with those on sickness benefits while helping claimants monitor their progress.
Shadow work and pensions minister Alex Cunningham said: "Even the Government's own research has shown that in its current form, the claimant commitment is not fit for purpose.
"Work coaches are struggling to properly support claimants with complex conditions and the Government must ensure that they receive the appropriate training."
The findings mirror long-standing concerns over some aspects of welfare reform.
Disability groups have criticised the so-called "conditionality" and focus on work, as well as a lack of understanding around mental health issues and other conditions.
A DWP spokesman said: "This voluntary trial showed that many people and work coaches responded positively to the claimant commitment and felt that it gave them access to the right support.
"All our work coaches receive thorough training on how to support people with disabilities and long term health conditions.
"They are able to tailor claimant commitments and ensure people are only asked to complete work related activity which is suitable and reasonable."